Thread tension adjusting device for a sewing machine

Abstract

A device including an axle rotatably supported in a sewing machine, a shaft fixed in parallel to the axle, one or more cams fixed on the axle, a lever having one end pivotally fixed and having the other end slidably engaged with the cam, and a gripping device including a pair of members disposed on the shaft and a spring disposed between the lever and the members so that a thread can be gripped between the members, and the lever can be caused to move toward or to move away from the members so that a tension force applied to the thread can be adjusted.

I claim: 
     
       1. An adjusting device for a sewing machine having an arm for accommodating said adjusting device, said adjusting device comprising a casing fixed in said arm of said sewing machine, an axle rotatably supported in said casing and having a first end extended outward of said casing, a shaft fixed in said casing in parallel with said axle, a knob fixed to said first end of said axle and extended outward of said arm of said sewing machine, at least one cam fixed on said axle, a lever having a first end pivotally fixed on said casing and having a second end slidably engaged on said shaft and having a protrusion formed on a middle portion thereof for slidably engaging said cam, and a gripping device disposed beside said second end of said lever and including a pair of members, one of said pair of members being fixedly secured to said shaft and the other member being slidably engaged on said shaft and means disposed between said second end of said lever and said pair of members for biasing said pair of members together so that a thread is gripped between said pair of members, and when said second end of said lever is moved toward or moved away from said pair of members when said axle and said cam are rotated, a tension force applied to said thread is adjusted. 
     
     
       2. An adjusting device according to claim 1, wherein said lever has a notch formed in said second end thereof, said gripping device includes a sleeve slidably engaged on said shaft between said lever and said pair of members and contacted with said second end of said lever and including a key formed thereon for engagement with said notch of said lever so that said sleeve is limited to slide longitudinally along said shaft, a disc threadedly engaged on said sleeve and including at least one recess formed therein, and an element slidably engaged on said shaft between said disc and said pair of members and including at least one leg formed thereon for sliding engagement with said recess of said disc, and wherein said means for biasing is a spring disposed between said element and said disc so that said tension force applied to said thread is adjusted when said disc is rotated relative to said sleeve.